问如何创建一个Rails 5模型，它实际上是在旅途中创建的数据库视图？

EN

class TagVisitSummary < ApplicationRecord

  belongs_to :tag

  default_scope { set_from_clause }

  def ==(other)
    self.class == other.class && attributes == other.attributes
  end
  alias :eql? :==

  def hash
    attributes.hash
  end

  private

  def self.set_from_clause
    query = TagVisit.select(:tag_id).group(:tag_id).select('SUM(visits) as total_visits').all
    from("(#{query.to_sql}) AS #{table_name}")
  end

  def self.columns
    cols = [ActiveRecord::ConnectionAdapters::Column.new('tag_id', nil, :integer)]
    cols << ActiveRecord::ConnectionAdapters::Column.new("total_visits", nil, :integer)
    cols
  end

end